The present invention relates to a method of joining two work pieces and more particularly relates to a method of joining two work pieces by arc welding.
In many conventional alternating current (AC) and direct current (DC) arc welding processes, first a path of contact is formed between selected surfaces of two work pieces. Then, at a point along the path of contact of the work pieces, a welding electrode is positioned relative to the work pieces to form an arc gap between the electrode and the work pieces. Usually an inert gas is supplied at the arc gap to provide an atmosphere which is suitable for electron flow across the arc gap. Then, a voltage is supplied across the arc gap to create a flow of electrons across the gap which provides a flow of power to the work pieces. The relative positions of the electrode and the work pieces are changed to make a single pass of the electrode over the path of contact of the work pieces while sufficient power is supplied to the work pieces to melt the material of the work pieces beneath the electrode. After the electrode has passed, the work pieces are welded together along their path of contact by dolidification of the melted material of the work pieces.
In conventional arc welding processes such as described above, sometimes precise control of the power density level at the work pieces is required, especially when welding relatively thin work pieces, to avoid overheating the work pieces since such overheating may result in a weld of poor quality. For example, if the work pieces are overheated, the resultant weld may be easily broken and/or the weld may not last very long when used under normal operating conditions. Also, the weld may not be fluid tight. Therefore, complex current programming of the arc welding power supply is used to precisely control the power density level at the work pieces. This current programming is achieved by using relatively complex, costly, and difficult to operate electronic components as part of the arc welding power supply. In order to maximize the versitility of the power supply, the current programming and corresponding electronics must be adjustable so that power density levels at the work pieces can be changed when welding different kinds of materials and when welding work pieces having different dimensions such as different thicknesses.